The objective of this research is to continue development of a physically-based parameterization of clouds and their radiative interaction for use by general circulation models (GCM's). The refined parameterization scheme will be implemented and tested using the Oregon State University 7-layer atmospheric GCM. Careful and detailed evaluation of the efficacy of the parameterization procedure will be carried out. This cloud/ radiation parameterization may reduce errors in the sea-surface temperature fields simulated by GCMS and will enable a quantitative determination of the potentially crucial cloud optical depth feedback process in numerical experiments of climate change due to increasing atmospheric carbon dioxide. Dr. Schlesinger will also involve two undergraduate students (Ms. Bogar and Ms. Bishop) in research tasks related to this grant. Ms. Bogar will asist in analyzing the inter-annual variability signal in GCM outputs. Ms. Bishop will work on modeling of climatic conditions during the previous interglacial (115,000 years ago). Besides gaining technical research experience, both undergraduates will benefit from working under close supervision of the PI and in collaboration with other graduate students and programmers.